Technical Field
The present invention relates to a distribution device of a combustion engine or internal combustion engine of a motor vehicle. The present invention relates more particularly to a system for lubricating a valve actuating device via a camshaft.
The present invention relates more specifically to the lubrication of the contact between a cam and a tongue which forms part of a valve actuating device.
Background Information
In motor vehicles provided with an internal combustion engine or combustion engine, distribution devices are installed therein so as to permit the intake of fresh air or gas into a chamber of a cylinder of the engine and then for the discharge of the burnt gases after combustion in the chamber. The distribution devices comprise valves which are mobile in translation in a cylinder head of the combustion engine. A valve is a mechanical member of the distribution system of combustion engines, permitting the intake of fresh gases and the discharge of burnt gases. Thus a distinction is made between an intake valve which separates the intake duct from the combustion chamber and an exhaust valve which separates the combustion chamber from an exhaust duct. The valve used in the motor vehicle engine is generally a stem valve or poppet valve comprising a stem which is extended at one end via a flared valve head which is designed to seal an orifice of the duct which opens into the combustion chamber.
The valve is generally actuated by a camshaft which is designed to push on the stem of the valve along the axis of the stem. To achieve this, the camshaft bears cams which press against a free end of the valve stem opposing the flared head, the shaft being driven in rotation about an axis substantially at right angles to the axis of the valve stem. The free end of the valve stem is thus pushed by a cam, which is fixed in terms of rotation to the camshaft, toward the combustion chamber of the cylinder to permit the opening of the fresh air intake duct or the burnt gas exhaust duct or evacuation duct. The stem slides in the cylinder head toward the combustion chamber to open an orifice of an air inlet duct or a burnt gas exhaust duct. The valve is then returned into position by one (or more) restoring springs.
The free end of the stem is generally of small section and the contact between the cam and the valve stem may be adversely affected which is liable to cause a malfunction of the combustion engine.
It is known to increase the contact section, for example by the addition of a contact cylinder at the free end of the stem, the contact cylinder being fixed to the stem and enabling the contact between the valve stem and the cam to be more reliable.
It is also known to place a contact tongue between the cam and the valve stem to ensure the transmission of the actuating movement of the cam to the free end of the valve stem. The tongue is generally composed of an arm which is mobile in rotation about an axis perpendicular to the axis of displacement of the valve stem and a tongue head which is designed to bear against the free end of the valve stem. During its rotational movement, the cam bears against a part of the arm of the tongue to cause a displacement in translation of the tongue head and thus of the end of the valve stem.
It is necessary, therefore, to lubricate the contact between the cam and the tongue in order to reduce wear and to make the operation of the valves reliable. To this end, it is known to hollow out lubrication ducts from the cylinder head, one downstream end thereof opening opposite the back of a tongue, for example, or of the cam, in the direction of circulation of the lubricating fluid.
The publication FR 2679601-A1 thus discloses a lubrication device for a cam of an internal combustion engine; the device comprising an oil supply duct connected to an oil supply manifold of the engine and opening into the surface of the cylinder head via an orifice, a jet of oil being sprayed thereby in the direction of the cam.
A drawback with the disclosed device is the requirement to bore such a duct for a cam of the engine and, in particular, between the various ducts present in the cylinder head.
A further drawback is the direction of the flow of oil which is sprayed to reach the contact surface of the cam.
The publication FR 2746846-B1 discloses a lubricating device comprising an arched portion in a chamber housing a camshaft. The arched portion comprises deflection surfaces to return the oil projected from a lubricating channel, which is hollowed-out from the camshaft toward the wall of the chamber, toward the surface of the cam.
A drawback is to create a chamber with larger dimensions in order to form the deflection surfaces.
A further drawback is the effectiveness of the device which does not return the oil in an accurate manner to the surface of the cam.